Perhaps the most effective antidote to 9/11 will prove to be 2/11, the day Hosni Mubarak conceded the game was up with his 30-year-old dictatorship and left town under military escort for the beach.

We’ve tried invasions of Muslim lands. We’ve tried imposing new systems of government on them. We’ve tried wars on terror. We’ve tried spending billions of dollars. What we haven’t tried is tackling what’s been rotten in the Arab world by helping a homegrown, bottom-up movement for change turn a U.S.-backed police state into a stable democracy.

This is the critical opportunity Egypt now presents. Islamist radicalism has thrived on the American double standards evident in strong support for the likes of Mubarak’s regime. It has prospered from the very brutal repression that was supposedly essential to stop the jihadists. And it has benefited from the reduction of tens of millions of Arab citizens to mere objects, shorn of dignity, and so more inclined to seek meaning in absolutist movements of violence.

If Westernized Egyptians and the Muslim Brotherhood can coexist in Egypt’s nascent Second Republic, and if a long-subjugated Arab people can show that it’s an actor of history rather than its impotent pawn, the likelihood of another Mohamed Atta walking the streets of Cairo will recede.

In 18 riveting days, Egypt has become a key to the unresolved 9/11 conundrum, the one President Obama promised to tackle by building bridges to the Muslim world, before Afghanistan diverted him.

“If we get Egypt right, it could be the best medicine to get rid of radicalism,” Mohamed ElBaradei, the Nobel Prize-winning opposition figure, told me.

In the Middle East you expect the worst. But having watched Egypt’s extraordinary civic achievement in building the coalition that ousted Mubarak, having watched Tahrir Square become cooperation central, and having watched the professionalism of the Egyptian army, I’m convinced the country has what it takes to build a decent, representative society — one that gives the lie to all the stereotypes associated with that dismissive shorthand “The Arab Street.”

In fact, post-Tahrir, let’s retire that phrase.

Speaking of streets, I watched them get cleaned the morning after the revolution. All the sweeping, dusting and scrubbing tempted me to suggest that there was no need to get carried away and try to turn the glorious metropolis of dust, Cairo, into Zurich. But Marwa Kamal put me right.

Kamal, 26, looked proud in her purple hijab. She was next to a sign saying, “Sorry for disturbance, we build Egypt.” I asked why she swept. “All the dirt’s in the past,” she said. “We want to clear out the old and start clean.”

A retired chemist, Mahmoud Abdullah, stepped in: “This is a very precious generation,” he told me, pointing at her. “They did what we failed to do.”

Right now Egypt has no president, no vice president, no constitution, no parliament and no significant police presence on the streets. But it has the meeting of generations between these two Egyptians; and it has a new sense of nationhood forged through countless other barrier-breaking discoveries of 18 shared revolutionary days.

Perhaps it was a good thing that, cocooned with his yes men, Mubarak proved so stubborn, locked in the prison of his formal Arabic and his hubris while language and nation unloosed themselves. I think it was over once the army declined to shoot. But by lingering, Mubarak gave Egyptians time to get to know each other.

Revolutions, like wars, have their interludes of boredom. They were filled with chat. And what did Egyptians find? Here’s one scene: Marwa Kassem, 33, Westernized, living in Geneva, talking to bearded Magdy Ashour of Muslim Brotherhood sympathies. She’d rushed to Cairo after the uprising began. He’d joined the protests after a friend was killed. If they’d passed each other in the street a month ago, each would have pulled back from the other, divided by fear.

He tells her he was arrested at regular intervals. How often? Sometimes twice a month. And? Ashour’s 14-year-old son is watching. He asks him to leave, saying “I want to show him freedom, not my cowardice.”

A frisson of tension stirs. Ashour stands up. They stripped me naked, he says, blindfolded me. He links his hands behind his back: this is how Mubarak’s security goons shackled him. They hung me from a hook on the wall, he says. Then came the electric shocks: to his toes, nipples, genitals.

There are tears in his eyes now. There are tears in Kassem’s, too. He pulls up his pants to his knee, revealing a terrible black scar on his calf. She cannot look. Why this treatment? “They wanted to know if I knew Osama bin Laden.”

What they both want now, this secular woman and this religious man, these two Egyptians, is a state of laws and rights.

Overcome 9/11 through 2/11: the road to reconciliation leads not through Baghdad or Kabul but through Tahrir.